When a transient switching center does not find a free line in a connection setup (for example, as a result of an occupied route), then the preceding switching center can be informed of this upon collaboration of a corresponding backward signaling. When the original connection is set up again in the preceding switching center via a different route, then this method is referred to as xe2x80x9creroutingxe2x80x9d or xe2x80x9ccrankbackxe2x80x9d.
Under normal load conditions, the probability that a connection can be successively set up through the network is enhanced with this rerouting method. Under high load conditions, however, the rerouting method leads to higher network blockings than given a connection set up without rerouting methods. At the same time, the rerouting generates an additional blind load under high load, which leads to a further worsening of the load situation in the network.
Up to now, this problem was solved in that the operator manually disconnects in this high-load cases.
This procedure has the following disadvantages:
A plurality of measured traffic data would have to be acquired.
This would not be practical without an involved and expensive traffic management center.
Manual interventions are susceptible to error.
The rerouting would have to be designationally shut off for the respectively affected traffic relationships, which is not practical manually in large networks because of the great plurality of traffic relationships.
The present invention is based on the object of avoiding the above described disadvantages.
In general terms the present invention is a routing method. A second routing attempt via an alternate path from an originating node is implemented for a call given an unsuccessful routing attempt via a preferred route, i.e. the call is offered a further alternate path to the destination node. The evaluation of the effectiveness of the rerouting is updated at each call per traffic relationship (originating/destination node pair), using an evaluation storing means. A decision is made on the basis of the evaluation as to whether the rerouting for this traffic relationship is to be maintained or throttled for following calls.
Advantageous developments of the present invention are as follows.
Effectiveness of the rerouting is evaluated in that a respective rerouting account is maintained as evaluation storing means per traffic relationship (originating/destination node pair). Given a successful routing of a call via an initially offered alternate route, the status of the account allocated to the traffic relationship of this call is incremented by a first amount. Given a rerouting required for a call, the status of the account allocated to the traffic relationship of this call is deincremented by a second amount. The rerouting is throttled fro a specific traffic relationship when the status of the account belonging to this traffic relationship falls below a specific threshold.
The present invention is also a rerouting system of a switching node in a communication network.
A rerouting means that, following an unsuccessful routing attempt of a call via a preferred route, a second routing attempt via an alternate path is implemented fro this call via an alternate path. A rerouting monitoring means that maintains an evaluation storing means per traffic relationship (originating/destination node pair) using the evaluation of the effectiveness of the rerouting is updated at each call, whereby the rerouting monitoring means decides on the basis of the updated evaluation as to whether the rerouting for this traffic relationship is to be maintained or throttled for following calls.
The rerouting monitoring means evaluates the effectiveness of the rerouting in that it maintains a respective rerouting account as evaluation storing means per traffic relationship (originating/destination node pair). The rerouting monitoring means, given a successful routing of a call via an initially offered alternate route, increments the status of the account allocated to the traffic relationship of this call by a first amount. The rerouting monitoring means, given a rerouting required for a call, deincrements the status of the account allocated to the traffic relationship of this call by a second amount. The rerouting monitoring means, throttles the rerouting for a specific traffic relationship when the status of the account belonging to this traffic relationship falls below specific threshold. The rerouting monitoring means throttles in that it temporarily suppresses the rerouting.